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Hydrofluoric acid (HF) has multiple applications and is widely used throughout industry, especially in organofluorine chemistry. Organofluorine compounds (eg, Teflon, freon, etc.) are synthesized using HF as the source of fluorine. Since this widespread use of HF invariably leads to human exposures, it is essential for clinicians to recognize that HF and fluoride-containing compounds are protoplasmic poisons that may result in deleterious systemic effects.

Hydrofluoric acid has been known for centuries for its ability to dissolve silica. The Nuremberg artist Schwanhard is given credit for the first attempt (in 1670) to use HF vapors to etch glass.42 Since then, HF has been developed for multiple uses in addition to glass etching, such as brick cleaning, etching microchips in the semiconductor industry, electroplating, leather tanning, rust removal, and the cleaning of porcelain.23,42 From 2005 to 2007, the American Association of Poison Control Centers (AAPCC) reported more than 2500 exposures to HF and 5 deaths. Hands are by far the most common exposure location. Exposures to HF are often unintentional and they can be an occupationally related hazard. The actual number of work-related poisonings from HF appears difficult to quantitate because of limitations in ICD (International Classification of Diseases) medical coding and lack of notification of regional poison centers by worksites.7

Hydrofluoric acid is also the most common cause of fluoride poisoning, although other forms of fluoride, including sodium fluoride (NaF) and ammonium bifluoride (NH4HF2), may also produce significant toxicity. Historically, sodium fluoride has been used as an insecticide, rodenticide, antihelminthic agent in swine, and a delousing powder for poultry and cattle. Ammonium bifluoride is mainly used in industrial inorganic chemistry, especially in the processing of alloys and in glass etching. Other fluoride salts are widely used in, for example, the steel industry, drinking water, toothpaste additives, electroplating, lumber treatment, and the glass and enamel industries.

The widespread use of HF and fluoride-containing compounds has resulted in significant toxicity. In 1988, an oil refinery in Texas released a cloud of hydrogen fluoride gas that resulted in 36 people requiring hospital treatment.42 The petroleum industry has since been plagued by similar HF incidents.95 NaF was responsible for the poisoning of 263 people and 47 fatalities when it was mistaken for powdered milk and unintentionally combined with scrambled eggs.52 These and other forms of fluoride salts can be converted to HF in vivo after ingestion. Consequently, many inorganic fluoride compounds can result in significant fluoride toxicity, especially when large exposures occur.

Hydrofluoric acid has unique properties that can cause life-threatening complications following seemingly trivial exposure. Anhydrous HF is highly concentrated (>70%) and used almost exclusively for industrial purposes. The aqueous form of HF, which generally ranges in concentrations from 3% to 40%, is commonly used in both industrial and household products.